The subject matter disclosed herein relates generally to muffling systems, and, more specifically, to muffling devices capable of providing pressure drops, acoustic improvements, and desirable flow properties.
In a gas turbine engine, air is pressurized in a compression module. The air channeled through the compression module is mixed with fuel in a combustor and ignited, generating hot combustion gases, which flow through turbine stages that extract energy therefrom for powering the fan and compressor rotors and generate engine thrust to propel an aircraft in flight or to power a load, such as an electrical generator.
In some gas turbine engines, a portion of the high-pressure air, such as, for example, bleed air from a compressor, may be extracted or bled from the compressor for various needs. These needs include, for example, compressor flow bleeding which may be used to improve operability as well as to provide turbine cooling, bearing sump pressurization, purge air, or aircraft environment control. The air may be bled off from the compressor using bleed slots located over specific portions or stages of the compressor.
In least some gas turbine engines, during engine operation occurring in some operating conditions, the compressor may pump more air than is required for needs including the combustion process. In order to manage operability of the engine and combustion performance, a portion of the excess bleed air from the compressor may be routed through bleed conduits and exhausted into the fan flow stream, engine exhaust, or to ambient. The pressure and temperature of the air stream bled from the compressor may be very high. For example, bleed air pressure may be greater than about 1375 kPa and the bleed air temperature may be greater than about 538 degrees C. A transient bleed valve system (TBV) system is sometimes used for bleeding and exhausting the air removed from the compressor. For example, the exhaust area of some conventional bleed systems may be oversized to lower the flow velocity at the exhaust location to assure that the acoustic requirements are met for the application. The exhaust area, as well as the relatively gently expansions between the source pressure and exhaust, may contribute to the relatively large size and/or weight of these systems.
The problem: In some applications (e.g., aircraft), it may be undesirable to use large and/or heavy components to reduce noise generated by bleed air and/or to direct bleed air into a fan flow stream or other locations.